Sensors and sensor modules worn on the body to measure or monitor biosignals, such as for example electrocardiogram (ECG), or photoplethysmogram (PPG) signals, frequently suffer from artifacts caused by motion of the body, especially when the sensors are intended to operate in continuous or ambulatory mode. A key technical challenge in such application environments is overcoming motion artifacts that significantly affect the measurements when the body is moving.
Patent applications US 2008/0208028 and US 2012/0143020 describe systems for the analysis of biopotential signals in which further motion artifact reduction or motion artifact handling techniques are used.
A technique of mitigating motion artifacts in PPG acquisition systems is described in “Artifact-resistant power-efficient design of finger-ring plethysmographic sensors”, by S. Rhee et al., IEEE Transactions on Biomedical Engineering, vol. 48, no. 7, pp. 795-805, Jul. 2001. The authors rely on mechanically stabilizing the LED and PD pair housed in a double ringed aluminum unit. This mechanical approach, however, is limited to PPG sensors that have a specific form factor; the ones that can be worn as a ring.
There is a motivation to improve current state of the art systems and methods for robust HR detection.